A shifter is used to interact with the transmission or rear axle of a truck or other vehicle to divert power from the engine between different gear ratios. Typically, in the rear axle of the vehicle, there will be only two gear ratios available. The vehicle engine will reach its peak power at a given rpm. Hence, each gear ratio will obtain its maximum efficiency at a set speed. By increasing the number of gear ratios, the number of speeds at which the truck may operate at peak power is increased. A two-speed rear axle of a truck or other vehicle doubles the number of gear ratios provided by its transmission. The goal is to keep the engine at its most efficient rpm as often as possible.
The driver of the vehicle uses a switch on the gear shift lever to choose a selected gear ratio for the rear axle. The shifter mounts to the rear axle and connects through a fork to a shifting mechanism in the rear axle. To shift between gears, the shifter exerts a force on the fork which would direct the shifting mechanism, which is attached to an output shaft, toward the desired gear ratio. The interaction of the gears in the rear axle will prevent any shifting of the output shaft until the clutch is disengaged or acceleration loading of the engine is removed. At that time, the output shaft will be diverted to the new gear ratio which will engage when the clutch is engaged.
Prior art shifters suffer from significant problems. It is important that the shifter be able to reliably detect the present state of the rear axle shifting mechanism. Prior art shifters use mechanical switches to detect the present gear ratio. These mechanical switches are subject to vibrations which occur during normal operation resulting in arcing or "switch chatter." Further, the prior art shifters need over one second to load the spring which provides the impetus to the fork, thereby decreasing the responsiveness of the shifter.
Therefore, a need has arisen in the industry to provide a reliable, responsive shifter.